1. Field of the Invention
The present invention relates to a sheet for mounting a workpiece and a method for making the same, and more particularly to a sheet with sealed or narrowed side surface pores for mounting a workpiece and a method for making the same.
2. Description of the Related Art
Polishing generally refers to wear control for a preliminarily coarse surface by the process of chemical mechanical polishing (CMP), which involves evenly dispersing a slurry containing fine particles on a top surface of a polishing pad, placing a workpiece against the polishing pad and rubbing the workpiece repeatedly with a regular motion. The workpiece is an object such as a semiconductor, a storage medium substrate, an integrated circuit (IC), an LCD flat-panel glass, an optical glass, or a photoelectric panel. A sheet is used to carry and fix the workpiece in place, and the quality of the sheet directly influences the polishing effect of the workpiece.
FIG. 1 is a schematic view of a polishing device having a conventional sheet disclosed in U.S. Pat. No. 5,871,393. The polishing device 1 includes a lower base plate 11, a sheet 12, a workpiece 13, an upper base plate 14, a polishing pad 15, and a slurry 16. The lower base plate 11 is opposite to the upper base plate 14. The sheet 12 is adhered to the lower base plate 11 through a backing layer 17, and the sheet 12 is used for carrying and fixing the workpiece 13. The polishing pad 15 is fixed on the upper base plate 14 and faces the lower base plate 11, and is used for polishing the workpiece 13.
The operation mode of the polishing device 1 is as follows. First, the workpiece 13 is disposed on the sheet 12, and the workpiece 13 is mounted by the sheet 12. Next, the upper base plate 14 and the lower base plate 11 are rotated in opposite directions, and meanwhile the upper base plate 14 is moved downwards, such that the polishing pad 15 contacts the surface of the workpiece 13, and a polishing operation for the workpiece 13 may be performed by continuously supplementing the slurry 16 and using the polishing pad 15.
FIG. 2 is a schematic perspective view of a conventional sheet. The sheet 12 has a top surface 121, a bottom surface 122, at least one side surface 123, and a plurality of communicating pores 124. The bottom surface 122 is adhered to the lower base plate 11 through the backing layer 17, and the top surface 121 is used for carrying and fixing the workpiece 13. During the polishing process, the slurry 16 enters into the sheet 12, and infiltrates into a space between the workpiece 13 and the top surface 121 of the sheet 12 to form a trace 131. A distance between the trace 131 and a side edge of the workpiece 13 is defined as an infiltration distance D. Within the infiltration distance D, the mounting force between the workpiece 13 and the sheet 12 is weakened, such that the workpiece 13 cannot be polished to be flat. Therefore, when the infiltration distance D reaches a predetermined value (of about 1 cm or 2 cm), the life of the sheet 12 ends, and the sheet 12 must be replaced.
As the sheet 12 is a single unit formed by cutting, some of the pores 124 open at the side surface 123 and are exposed at the side surface 123, thus leading to the following disadvantage. During the polishing process, the slurry 16 will rapidly enter into the interior of the sheet 12 through the pores 124 that open at the side surface 123, and simultaneously rapidly infiltrate into the space between the workpiece 13 and the top surface 121 of the sheet 12. As a result, the infiltration distance D quickly reaches the predetermined value (of about 1 cm or 2 cm), thereby diminishing the effective life of the sheet 12, which must thus be replaced relatively frequently, incurring additional time and cost.
Therefore, it is necessary to provide an innovative and inventive sheet for mounting a workpiece and a method for making the same to solve the above problems.